. Elements of comparative zoology. Zoology. REPTILES. 343 The body is more or less completely covered with scales, and the toes, when present, bear claws. The scales differ from those of fishes in being outside of the outer layer of the skin. These scales differ much in ar- rangement, etc. The large plates covering the carapace of the tur- tle are but enlarged scales, while the bony armor of the alligator is composed of scales, rendered more protective by the development of bone in the deeper layer of the skin. In the snakes the scaly covering is periodically shed. By the greater development o
. Elements of comparative zoology. Zoology. REPTILES. 343 The body is more or less completely covered with scales, and the toes, when present, bear claws. The scales differ from those of fishes in being outside of the outer layer of the skin. These scales differ much in ar- rangement, etc. The large plates covering the carapace of the tur- tle are but enlarged scales, while the bony armor of the alligator is composed of scales, rendered more protective by the development of bone in the deeper layer of the skin. In the snakes the scaly covering is periodically shed. By the greater development of the neck the heart is carried back to a greater distance from the head than in the Batrachia. In all except the alligators the heart is three-chambered, and in these the ventricle is incompletely di- vided into two. There are two aortic arches (fig. 141), but the left one, which also supplies the stomach, is smaller where it joins its fellow to form the dorsal aorta. The blood is 'cold,' or rather it is variable in temperature, varying with that of the air or water in which the animal lives. The brain is small, no part being extremely developed, and the optic lobes touch, or may touch, each other in the median line. In snakes, lizards, and turtles the cerebel- lum is small; in the alligators it is FIG. 141.—Arterial Circulation of Turtle. a, right aortic arch; b, bronchus; /, artery to fore limb; h, artery to hind limb; p, pulmonary artery; r, renal arteries; s, arteries to stomach; t, trachea; 1, 2, 4, persisting aortic arches. Compare with fig. 117, Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Kingsley, J. S. (John Sterling), 1854-1929. New York, H. Holt and Company
Size: 896px × 2788px
Photo credit: © Paul Fearn / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1900, booksubjectzoology, bookyear1904
